HUNG, FRANCISCO RODOLFO. Capillary Condensation and Freezing of
Simple Fluids Confined in Cylindrical Nanopores. (Under the direction of Keith E.
Gubbins).
We present a molecular simulation study aimed at understanding the phase
behavior of pure simple fluids, when they are confined inside nanopores of
cylindrical geometry. In this situation, new surface-driven phases can appear, and
phase transitions typical of bulk systems (gas-liquid, freezing) can be shifted to
different conditions. A fundamental understanding of these phenomena is
necessary for applications in separations, catalysis and nanotechnology. Studies of
these phenomena can also provide important insights on the effect of surface
forces, confinement and reduced dimensionality on the phase behavior of host
molecules. We have performed two independent, but directly related studies: (1)
freezing of carbon tetrachloride within multi-walled carbon nanotubes (MWCNT)
of different diameters, and (2) capillary condensation and freezing of krypton
within templated mesoporous silica materials (MCM-41). MWCNT and MCM-41
are representative of materials with strongly and weakly attractive walls,
respectively. In the first part of this project, the structure and thermodynamic
stability of the confined phases, as well as the temperatures and the order of the
phase transitions were determined using dielectric relaxation spectroscopy
measurements and Monte Carlo simulations in the grand canonical ensemble. A
rich phase behavior with multiple transition temperatures was observed for such
systems. In the second part of this project we developed realistic, atomistic models
of MCM-41 type materials that include pore surface roughness and morphological
defects in agreement with experimental results. Grand Canonical Monte Carlo
simulations show that these variables have a profound influence on gas-liquid and
freezing transitions in confinement.
A Desirée y Arianna,
a mi familia, especialmente mis padres,
a Dios y la Virgen Milagrosa.
Gracias por bendecir mi existencia.
To Desirée and Arianna,
to my family, especially my parents,
to God and Virgin Mary.
Thanks for blessing my life.
… and to Murphy.
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Biography
Francisco R. Hung was born on November 5, 1973 in Caracas, Venezuela, to his
parents Yun Wun Hung and Lai Ngor de Hung, both originally from China. He
was raised in Caracas, along with his older brothers Daniel and Julio. Francisco
attended Universidad Simón Bolívar in Caracas to study Chemical Engineering,
earning a scholarship from Pequiven (the Venezuelan petrochemical industry) in
1991. Francisco graduated cum laude and first of his class in 1996. He then started
his graduate studies in Chemical Engineering at Universidad Simón Bolívar, and at
the same time, he was hired as a Lecturer by the Department of Thermodynamics
and Transport Phenomena. He was in charge of teaching a number of
undergraduate courses, such as Thermodynamics and Transport Phenomena
laboratories, while taking graduate courses and doing his research project. Under
the supervision of Professor Erich A. Müller, Francisco studied adsorption of water
vapor and methane mixtures on activated carbons using molecular simulation
techniques. He obtained his M.S. in Chemical Engineering (honor mention) from
Universidad Simón Bolívar in 1999, and became an Assistant Professor. Francisco
started his Ph.D. studies in the Department of Chemical Engineering at North
Carolina State University in 2000. He joined Prof. Keith E. Gubbins’ research
group, where he carried out the work presented here. After defending his
dissertation, Francisco will join Prof. Juan J. de Pablo’s research group at the
University of Wisconsin-Madison, to work as a postdoctoral research associate.
Twelve days before coming to Raleigh, on July 29, 2000, Francisco married his
sweetheart, Minerva Desirée Vignola, who was then a journalist working in a radio
station in Caracas. They are the proud and happy (and sometimes exhausted)
parents of Arianna, a fully-energetic and always-smiling little girl who was born in
Cary, North Carolina, on May 1, 2003.
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